Treatment options for bleeding episodes in patients undergoing immune tolerance therapy

Inhibitors to factor VIII develop in 4-20% of haemophilia A patients, with the percentage rising to 52% in certain subpopulations. The management of inhibitor patients is directed toward stopping acute haemorrhages, providing short-term haemostasis before and after surgery, and inducing immune tolerance to factor VIII (immune tolerance therapy or ITT). Several different protocols have been used for ITT, but they are all centred around ongoing exposure to high doses of factor VIII. High responders (those patients with a large increase in inhibitor level after exposure to factor VIII) are the prime candidates for ITT, but low responders may also benefit from this treatment. It is often necessary to treat bleeding episodes during ITT, because elimination of inhibitors may require many years of therapy. Treatment of haemorrhages in inhibitor patients is reviewed for both low and high responders during ITT and in the absence of ITT. The choice of clotting agent for inhibitor patients who have not yet responded to ITT depends on current and past inhibitor levels, the severity of the haemorrhage, the site of the haemorrhage or the setting in which it occurs (e.g. surgical), and the extent of inhibitor cross-reactivity with porcine factor VIII. Patients with high-titre inhibitors experiencing a critical haemorrhage are generally best managed with bypassing agents (AUTOPLEX T or FEIBA VH), porcine factor VIII or rFVIIa.